If you're like us, you're probably thinking a lot about how this year's flu season might affect you and your community. To help you out, we at Google.org are excited to announce the expansion of Google Flu Trends to 16 additional countries, including much of Europe. We've also made the site available in 37 languages. Flu is a global threat, affecting millions worldwide each year, so we're pleased to make this tool available in more regions and languages.

Last November, we launched Google Flu Trends in the United States after finding a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms. By tracking the popularity of certain Google search queries, we are able to estimate the level of flu, in near real-time. While some traditional flu surveillance systems may take days or weeks to collect and release data, Google search queries can be counted immediately. Google Flu Trends provides an additional surveillance tool that may help public health officials and the public make more informed decisions about preparing for the flu season.

In the past year, we've expanded our coverage to include Mexico, New Zealand and Australia and have continued to see a good correspondence between our estimates and official flu activity data. In fact, our analysis of last season shows that Google Flu Trends had a close 0.92 correlation with official U.S. flu data.

An important aspect of Google Flu Trends is that we filter out terms that may be popular because people hear about them in the news. What we do not use in the models is a term like [swine flu] since people are more likely to type that into Google because they want to know more information about it, given the news headlines, and not because they actually have H1N1 or swine flu. For more information about how we built this model, take a peek at this video:

If you visit Google Flu Trends for the U.S., you'll notice that the flu season is starting early this year. For tips on how to stay healthy this season, please visit our friends at the U.S. CDC and the ECDC.